Abstract

We report laser photoelectron spectra of the ${\text{SiCH}}_2^{-},{\text{SiCH}}_3^{-}$ , and ${\text{SiCH}}_4^{-}$ anions and their perdeuterated analogues at an instrumental resolution of 30 cm⁻¹. These anions were prepared from tetramethylsilane by using a flowing afterglow ion source equipped with a microwave discharge cavity. The spectra yield vibrational frequencies for both the anions and the corresponding neutral molecules, and they also yield the electron affinities. These data indicate a doubly bonded silylidene structure for SiCH₂ and a singly bonded methylsilylene structure for SiCH₄. Both the singly bonded S–CH₃ and the doubly bonded HSi=CH₂ isomers are observed. These results provide new information concerning multiple bonding between silicon and carbon. In addition, they illustrate the ability of this technique to provide direct spectroscopic identification of isomers present in the flowing afterglow ion-molecule reactor.

© 1992 Optical Society of America